In deposition-type arc-welding systems, an arc-welding burner fuses a consumable electrode and deposits the weld material in a pool in the gap between a pair of workpieces which generally are deposited horizontally so that the upper surface of the pool, as it is formed, is at a distance from the end of the welding electrode. This space or gap is spanned by the welding arc.
In welding technology it is known to use the arc voltage as a measured-value input or signal for the voltage control of the distance between the electrode end and the upper surface of the pool so as to maintain this distance constant, effecting high welding speed with the formation of the weld bead or seam as uniformly as possible.
This is accomplished by changing the distance between the electrode end and the upper surface of the pool of weldment with a change in the measured value of the arc voltage, the position of the electrode end being modified accordingly to restore the set-point value of the spacing.
This system has, it has been found, the disadvantage that the spacing between the electrode end and the upper surface of the pool is maintained constant by lowering the electrode end toward the pool when the level of the upper surface of the weldment pool falls with respect to the upper surface of the workpieces flanking the pool. In other words, if the pool of weldment is formed in the crevice between juxtaposed edges of the two workpieces, and the surface of the pool of weldment falls within this crevice and hence the distance between the upper surfaces of the workpiece adjacent the crevice and the upper surface of the pool increases, the automatic control means previously described maintains the spacing between the electrode end and the upper surface of the pool by lowering the electrode end. While this succeeds in maintaining substantially constant the weld performance or welding power of the weling burner, it results in a weld seam which tends to become thinner progressively with an increasing depth of the root of the crevice or widening of the latter. Ultimately, the weld will break through the underside of the crevice.
Such a breakthrough during the welding process has been prevented heretofore by supporting the pool of wledment below the crevice with a metal plate or a like pool support. Naturally, the need to provide for such an additional support to prevent breakthrough is time-consuming and, indeed, the use of such support may not even be possible in many cases, e.g. because of the nature of the workpiece to be welded.
Naturally, it is difficult to ensure extremely small tolerances of the end faces of a pair of workpieces which are to be joined together by deposit welding so as to avoid all variations in the level of the welding pool, for a constant rate of deposition, relative to the upper surfaces of the workpieces adjoining the welding crevice.
As prior art which may be material to the present application, reference may be made to U.S. Pat. No. 3,511,966, No. 1,826,186 and No. 3,426,175, to Russian Pat. No. 322,247 and No. 335,055 and to German Pat. No. 1,957,508.